A-24 ANSWERS Chapter 8 SECTION 8.1, PAGE 461 71. Angles 3, 4, and 7 each measure ° 130 ; angles 1, 2, 5, and 6 each measure ° 50 . 72. Angles 2, 4, and 5 each measure ° 120 ; angles 1, 3, 6, and 7 each measure ° 60 . 73. Angles 1, 4, and 7 each measure ° 20 ; angles 2, 3, 5, and 6 each measure ° 160 . 74. Angles 2, 5, and 6 each measure ° 25 ; angles 1, 3, 4, and 7 each measure ° 155 . 92. Sometimes true. A triangle must always contain at least two acute angles. Some triangles contain three acute angles. 94. Sometimes true. Alternate exterior angles are only supplementary when each is equal to ° 90 . 95. Sometimes true. Alternate interior angles are only complementary when each is equal to ° 45 . 104. SECTION 8.5, PAGE 515 This figure contains the answers to Exercises 9 and 10. 10. 9. B9 C9 A9 A C B m A9 B9 C9 l This figure contains the answers to Exercises 11 and 12. A B C D A9 D9 C9 B9 m l 12. 11. B9 A9 C9 D9 This figure contains the answers to Exercises 13 and 14. D9 C9 B9 A9 A9 C9 D9 D A B C B9 m l 13. 14. This figure contains the answers to Exercises 15 and 16. C9 m C C9 l 16. 15. 105. a) B A D C E Other answers are possible. SECTION 8.2, PAGE 471 33. = = = = m m m m 1 90°, 2 50°, 3 130°, 4 50°, = = = = m m m m 5 50°, 6 40°, 7 90°, 8 130°, = = = = m m m m 9 140°, 10 40°, 11 140°, 12 40° 34. = = = = m m m m 1 51°, 2 59°, 3 70°, 4 70°, = = = = m m m m 5 51°, 6 110°, 7 51°, 8 129°, = = = = m m m m 9 70°, 10 110°, 11 129°, 12 51° SECTION 8.4, PAGE 496 61. b) = = = = V aV abV abV ab ; ; ; ; 1 3 2 2 3 2 4 2 = = = V a b V ab V b ; ; 5 2 6 2 7 3
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